This invention relates generally to electrical receptacles and, more particularly, to certain new and useful improvements in a safety shutter mechanism for use in such receptacles to prevent the entry of small objects such as screwdrivers and paper clips which may be manipulated by an inquisitive child into the slots of such receptacles.
Electrical receptacles are utilized in large numbers both in industry and in the home to provide ready access for electricity to power a variety of devices including motors, lamps, heating elements and amusement articles. These devices are connected to a source of electric power by means of an electric power cord having a plug at an end thereof, the prongs of the plug being inserted into matching slots of the receptacle.
A problem arises in that the slot of the receptacle will admit other objects in addition to the aforementioned prongs. For example, the blade of a screwdriver or of a jackknife, a paper clip, and a metal tang or protrusion of a child's toy may all fit within the receptacle slot. Such metallic electrically-conducting objects present the hazard of electric shock to an inquisitive child who may deliberately or inadvertently insert such an object into the slot.
The desirability of a safety mechanism for preventing electrical shock upon entry of such objects into electrical receptacles has been previously recognized. The numerous prior proposals for such mechanisms, however, have not performed satisfactorily, or have been complicated or difficult to assemble, or expensive to manufacture and, accordingly, either have not reached or have not been accepted by, the general public. Thus, in spite of the numerous prior attempts to provide a commercially acceptable safety receptacle, and the long-sought need for such a device, it is believed that no such device has achieved commercial success.
In one such prior proposal, insertion of a prong or blade through one receptacle slot actuates a switch bringing electricity to the opposite terminal, thus requiring simultaneous insertion of blades into both slots in order to accomplish electrical contact. This device is disadvantages because proper assembly is critical and difficult and the additional switches result in added heat rise in operation. In another prior proposal, a shutter in the form of a disc includes a cam surface operated only by the ground pin of an appliance plug, the ground pin rotating the disc to open the receptacle slots. This device is disadvantageous because it requires the use of an appliance plug with a grounding pin for operation.
Other prior proposals for shutter mechanisms in electrical receptacles are shown in U.S. Pat. No. 2,548,536 (1951) and British Pat. No. 508,248 (1939). While the operation of the devices shown in these patents is similar to that of the present invention, the structure of U.S. Pat. No. 2,548,536 (1951) is disadvantageous from the standpoint of reliability in that it requires the parts to rock into alignment in order to open the receptacle slots, which may be difficult. British Pat. No. 508,248 (1939) is disadvantageous because its structure is designed for use only with a plug having two blades and would not be capable of use with a plug also containing a grounding prong, which is conventional in the United States.
It is therefore an object of this invention to provide a novel electrical receptacle wherein the receptacle slots are shuttered so as to prevent inadvertent electrically-conducting contact with the receptacle terminals.
Another object of this invention is to provide in a novel electrical receptacle a safety shutter mechanism providing a barrier to entry through the receptacle slots except upon the simultaneous insertion of a blade or prong into each of the slots.
Another object of this invention is to provide in a novel electrical receptacle a safety shutter mechanism in which two identical oppositely disposed slides, each including a barrier surface and a cam surface, are arranged so that both a barrier surface and a cam surface are in register with each of the receptacle slots.
Another object of this invention is to provide a novel electrical receptacle having a safety mechanism for the receptacle slots which eliminates the aforementioned disadvantages of the prior proposals for such a safety mechanism.
Another object of this invention is to provide in a novel electrical receptacle a safety shutter mechanism which is simple in its construction, easily assembled, reliable and trouble-free in operation and may be manufactured at low cost.
Objects and advantages of the invention are set forth in part herein and in part will be obvious herefrom, or may be learned by practice with the invention, the same being realized and attained by means of the instrumentalities and combinations pointed out in the appended claims.
The invention consists in the novel parts, constructions, arrangements, combinations and improvements herein shown and described.